Abstract
We explore the evolution of supermassive black holes (SMBH) centered in a circumnuclear disk (CND) as a function of the mass supply from the host galaxy and considering different star formation laws, which may give rise to a self-regulation via the injection of supernova-driven turbulence. A system of equations describing star formation, black hole accretion and angular momentum transport was solved for an axisymmetric disk in which the gravitational potential includes contributions from the black hole, the disk and the hosting galaxy. Our model extends the framework provided by Kawakatu et al. (2008) by separately considering the inner and outer part of the disk, and by introducing a potentially non-linear dependence of the star formation rate on the gas surface density and the turbulent velocity. The star formation recipes are calibrated using observational data for NGC 1097, while the accretion model is based on turbulent viscosity as a source of angular momentum transport in a thin viscous accretion disk. We find that current data provide no strong constraint on the star formation recipe, and can in particular not distinguish between models entirely regulated by the surface density, and models including a dependence on the turbulent velocity. The evolution of the black hole mass, on the other hand, strongly depends on the applied star formation law, as well as the mass supply from the host galaxy. We suggest to explore the star formation process in local AGN with high-resolution ALMA observations to break the degeneracy between different star formation models.
Highlights
Supermassive black holes (SMBH) are observed in the centers of virtually all galaxies, and their properties are tightly correlated to the mass of the stellar bulge and its velocity dispersion (Magorrian et al 1998; Ferrarese & Merritt 2000; Gebhardt et al 2000; Graham et al 2001; Merritt & Ferrarese 2001; Tremaine et al 2002; Häring & Rix 2004)
For unregulated star formation we have ≡ 0 so that the star formation model is insensitive to an increased turbulent velocity (compare Eq (11)). θ is a free parameter, whereas Ψ has been chosen in such manner that the final stellar masses are roughly equal for all pairs of (θ, Ψ), to ensure comparability of the different models
We have extended their model by separately considering the inner and outer disk and by considering the impact of a non-linear relation between the star formation rate, the gas surface density and the turbulent velocity
Summary
Supermassive black holes (SMBH) are observed in the centers of virtually all galaxies, and their properties are tightly correlated to the mass of the stellar bulge and its velocity dispersion (Magorrian et al 1998; Ferrarese & Merritt 2000; Gebhardt et al 2000; Graham et al 2001; Merritt & Ferrarese 2001; Tremaine et al 2002; Häring & Rix 2004). Similar conditions have been found for a lensed quasar at z = 4.1 (Riechers et al 2008) and the Cloverleaf quasar at z = 2.56, where warm molecular gas was detected both in CO (Bradford et al 2009) and HCN (Riechers et al 2011) Based on these even though limited observations, we may conclude that circumnuclear starburst rings may play a significant role in connecting black hole growth and star formation both at low and high redshift.
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